A series of mystery novels centered around a gay sleuth that dishes up compelling cases and manages, from time to time, to break your heart is a little like the Spanish Inquisition: To reference Monty Python, no one expects it.

Yet, here's author Marshall Thornton with the just-released fifth book in his "Boystown" series, a novel titled "Murder Book." It's a doubly apt title. On one level, it refers to a compendium of records about a series of killings targeting gays, many of them young male hustlers; on another level, the title underscores that though murder is at the heart of all the mysteries in the series, this time it's personal.

The adventures of private eye Nick Nowak began with novellas that were packages two or three to a volume. The place is Chicago; the time is the early 1980s; the boys of Boystown are hot and always happy for a friendly tussle, and Nick Nowack is a naturally good-looking sort who gets plenty of attention.

The "Boystown" series name comes from the gay section of Chicago where Nowak lives and sometimes plies his trade. In many ways, it's a tough time to be gay, and prior to the start of the first story, Nowak and his ex have broken up following an anti-gay attack. Nowak's former boyfriend insisted on telling the cops the particulars of the case; the problem with this is that, at the time, Nowak himself was a cop.

But not for long. Once word got out, Nowak found himself shunned by his fellow boys in blue. Even as a detective, he comes in for homophobic harassment from Chicago's finest. But love has a way of blossoming even in the desert of prejudice; Nick's new boyfriend, Bert Harker, is another Chicago cop. Though deeply closeted, Harker entered into a relationship with Nowak.... but now comes the heartbreak: As the AIDS epidemic dawned, Harker began to display alarming symptoms that put him on disability.

Starting with the fourth volume in the series, "A Time for Secrets," the Nick Nowack stories left the shorter format behind in favor of novel-length tales, one to a book. The newly-released fifth book takes place in the autumn of 1982, and a sense of foreboding asserts itself on the very first page when Nowak comes home to find Harker missing. Soon enough, his worst fears are confirmed; Harker has become the latest victim of the "Bughouse Slasher," the serial killer who preys on gay men.

But Harker has left behind a body if evidence in the "murder book" he was unofficially working on. Even as the city of Chicago is seized by terror in the wake of bottles of Tylenol being poisoned with cyanide, and the police force is stretched too thin to investigate Harker's murder, Nowak pursues the slenderest clues to the fatal conclusion that Harker didn't live to share: The identity and whereabouts of the Bughouse Slasher.

Marshall Thornton chatted with EDGE recently about his gay gumshoe, the latest twist in his ongoing adventures, and what's next.

EDGE: One of the rules for writing is to "kill your darlings." You’ve done that in this new book, but what led to the decision to do it now and in this way?

Marshall Thornton: Well... I’m not one of those writers who says ’my character made me do it.’ But in a way he did.

The feedback from readers suggested they were expecting a typical, hospital-bound AIDS death. Sort of the ’80s, gay version of "Love Story." I don’t have any problem with that from a writing perspective, but as I’d constructed Harker’s character, I didn’t think he’d have much patience for it. I also felt that he was acutely aware of his impending death and that he’d want to make some sense of his life.

I didn’t get the idea until I was half way through "Boystown 4," and when I did, I saw that I’d been setting it up since the second book. I suppose I could have waited, slipped in another book, but I don’t know what I would have done with Harker. That he knew he was dying really trumps any other plot line I could have thought up.

EDGE:You’ve also re-introduced series nemesis The Bughouse Slasher in this installment. Again, I was a little surprised to see him back so soon. I thought maybe you’d let him lurk for a few books more?

Marshall Thornton: The way you phrase the question is interesting. My perception of time is probably very different from a reader’s. The books have been coming out one a year since 2009.

On the one hand, I’m very aware of "book time," which for The Bughouse Slasher was a little more than a year between appearances. At the same time, there were three years of writing between his appearances, so it didn’t feel soon to me. I could have let him lurk... but then I think I’m happier that you were a little surprised. If he’d killed anyone else it might have become too obvious what was about to happen.

EDGE: You also reference an infamous incident from the 1980s, the poisoning of Tylenol capsules with cyanide, a crime that has never been solved. Will you be building other landmark events of the decade into forthcoming stories?

Marshall Thornton: Yes. That’s the largest incident I’ve used and the most directly involved with the plot, but I’ve been tossing smaller incidents in all along.

I’m not sure at this point if other famous incidents will be crucial to my plots, but I do always add that kind of detail. And, certainly, information about AIDS - which tended to hit Chicago a little later than New York and San Francisco - will be factoring in.

EDGE: Both this latest case and the previous entry are full-length novels. Will you be sticking to this format? Or do you plan to alternate the novels with the anthologies of novellas?

Marshall Thornton: I think readers prefer novels. My plan is to stick with novels, but I’ve learned to never say never. Whenever I do say never I end up doing whatever I said I wouldn’t do in about three weeks.

So... possibly I’ll write more short stories. I’m most likely to write a single, e-book only story as I did with the prequel story "Little Boy Dead." Though at the moment I don’t have any plans for something like that.

EDGE: Time is moving forward in the Boystown series. Do you plan to keep the installments at pretty regular intervals or will we be seeing some jumps - two years later, five years later, that sort of thing?

Marshall Thornton: "Boystown 6" is set in January of 1984, a little more than a year after "Boystown 5." Given Nick’s emotional state at the end of this book it seemed a good time to make a leap. There may be leaps in later books; however, it depends a lot on Nick’s emotional state.

EDGE: Are you thinking you’ll move into the 1990s eventually or is this series really a creature of the ’80s?

Marshall Thornton: I’m not sure at this point. I’d love to get all the way to the new meds in ’95/’96, that was such a remarkable change for a lot of people. It would interesting to see Nick go through that period. But, at the rate I’m going, that’s a lot of books.

EDGE: What’ll be next for Nick Nowak, in ’Boystown 6?’

Marshall Thornton: Quite understandably, he’s been pretty unhappy in between the books. He’s let his private investigation business go to pot. He’s lost his apartment and has taken a job bartending at Irving’s "L" Lounge.

One day, the least likely person from his life shows up and asks him to investigate the very un-suspicious death of a priest. A death that quickly becomes suspicious.

EDGE: What’s next for you? Anything non-Nick coming up?

Marshall Thornton: I have a romantic comedy called "The Ghost Slept Over" coming out in the fall with MLR Press. It’s about a failed actor, Cal Parsons, who travels to rural New York to claim the estate of his estranged ex-partner. When he gets there he finds something he wasn’t expecting...the ghost of his ex.

Marshall Thornton has just seen Book 6 in his '80s gay detective series published; he's also got a new comic novel out. The versatile novelist chats with EDGE about noir, humor, and the dark days of The Plague.